The present invention relates to semiconductor photonic, discrete optic, integrated optic, and opto-electronic devices. In particular, the present invention relates to active photonic device such as an optical amplifier, laser, light-emitting device, plasmonic optical waveguide based device, photodetector, optical intensity or phase modulator, optical switch (controlled electrically), wavelength converter, and all-optical device (including devices that are controlled optically, such as all-optical wavelength converter, all-optical switch, all-optical logic gate, and all-optical signal processing device), all of which involve optical beam interaction with an active optical gain/absorption medium in the device and all referred to collectively as active photonic devices for the purpose of this invention. These devices can be used to perform optical signal processing and are also referred to as optical signal processing devices. While they are devices that have different functionalities, they can share the same general device structure that give high device operating efficiency or high device performance. This general device structure capable of giving high device efficiency or high device performance is the focus of the present invention. Such active photonic devices are required for forming a photonic subsystem, converting electrical signals into optical signals and vice versa, and manipulating optical and electrical signals, so that the light beam can be used to transmit information over an optical communication system. The light source in an optical communication system typically involves a semiconductor laser. The transmission and propagation of light typically involves an optical fiber or optical waveguide. The receiver in an optical communication system typically involves a photodetector. Optical amplifier is typically needed to amplify the power of the optical beam to compensate the beam's power loss during beam's propagation. Active photonic devices are devices that perform functions such as optical amplification, light emission, optical detection, beam's intensity modulation, beam's phase modulation, electro-optical beam switching, all-optical beam switching, and beam's wavelength or spectral conversion, as is known to those skilled in the art. They are functions that typically require energies to be consumed (e.g. consumption of electrical or optical energy) or exchanged (e.g. exchange between optical energy and electrical energy).
The typical active photonic devices available currently such as optical amplifiers based on utilizing semiconductor quantum wells in compound semiconductors with direct energy bandgap typically have high electrical power consumption. For example, a typical optical amplifier available in the market today to amplify the power of an optical beam (at the optical wavelength of 1550 nm) requires over 100 milli-Ampere of electrical current to power up under a 2V applied voltage. This means over 200 mW of electrical power just to power an optical amplifier for the amplification of one optical beam. This power is very high especially when the optical amplifier is used in an electronic-photonic integrated circuit (EPIC) or photonic integrated circuit (PIC), as the total power consumption of a large electronic microprocessor chip with millions of transistor is only a few Watts. Viewing the optical amplifier as just one active photonic device, its power requirement is extremely high when compared to a single electronic transistor, considering the fact that the typical power consumption of an electronic transistor in a typical micro-processor-type electronic chip is in the 0.2 to 1 micro-Watt (200 to 1,000 nanoWatts) range per transistor at the operating speed of 1 GHz. Beside power consumption, it is also of interest to reduce the physical size of active photonic devices so that they are not too large comparing to the size of electronic devices. Thus, active photonic devices capable of operating with low power consumption or have small device size would be of great interest to make it compatible with CMOS circuits. Achieving low power consumption and small device size is part of the device efficiency. In addition, the device structure must have low optical losses such as due to unwanted optical absorption or scattering. Active photonic devices that have low operating power consumption, small device size, and preferably low device insertion loss are referred to collectively as high-efficiency or high-performance active photonic devices.